Spec clarification: sampleTime on XrFacialExpressionsHTC

The spec for [XrFacialExpressionsHTC](https://registry.khronos.org/OpenXR/specs/1.1/html/xrspec.html#XrFacialExpressionsHTC) states:
> `XrFacialExpressionsHTC` returns data of a lip facial expression or an eye facial expression.

I would think that this means that all of the fields are set by the runtime.

However, some applications I've seen are actually setting the `sampleTime` field to `XrFrameState::predictedDisplayTime` before passing `XrFacialExpressionsHTC` to the `xrGetFacialExpressionsHTC` call.

The only information about `sampleTime` in the spec is:
> `sampleTime` when in time the expression is expressed.

Please clarify if `sampleTime` is to be set by the runtime or the application.

Start with the linked OpenXR 1.1 specification section for XrFacialExpressionsHTC and the definitions of sampleTime, then review the xrGetFacialExpressionsHTC call context. Done means the specification explicitly states whether sampleTime is supplied by the runtime or application, with wording that removes the ambiguity.

Written by the indexing model from the issue text.